Hi, uhm just a little theory about tobi,
I think tobi might be Obito, if you dont know who obito is read kakashi gaiden,
but anyway, i think he is cause one, he obito gave his left eye to kakashi, two, madara uchiha would be dead -.-, and if he was alive he would be like 2 hundread years old, and 3 i saw this picture on the internet of tobi taking of his mask to kakashi and naruto and it was like
obito: Hey Kakashi! ^_^
kakashi: obito...!
obito: hey sensei! did you shrink?! , (he said this to naruto)
naruto: who is this guy? T_T
and yeah... thats just my theory ^_^
if you disagree, SAY SO! T_T

Maybe it has something to do with the outcome of Kakashi's training on wind element transfiguration. Probably Kakashi and Yamato told Naruto not to tell anyone about the the outcome of the training, which is why Naruto instantly refused to answer the frog's question.

HUGE SPOILER AHEAD
read only if your that curious, and know who
Rin is from Kakshi Gaiden.

Spoiler Alert! Click to show or hide

Okay, so we all know that Minato Namikaze (4th Hokage) was once a team leader, and on that
team was Kakashi, Obito, And Rin.
If you had read kakashi gaiden then you should know what had happend
on that last dreadful mission,
obito "died" , and kakshi lived on his life in solitude.